This area is one I grew up around, and have seen all manner of craft fly over, as there are more than one airstrip nearby. I myself have flown over this area, more than once.
So, "Yes, I had some knowledge of where in the sky these things were."
There are a number of problems with this line of reasoning. The main one is that it completely ignores the possibility of you ever being mistaken. It means you are absolutely, completely aware of all situations capable of creating confusion and absolutely completely aware of all conventional crafts and natural phenomena above you. You are never mistaken, not even by an odd angle or weird observing conditions. The way I see it, it doesn't matter how small the odds of you being mistaken are. The odds are always there and all it takes to create an UFO sighting is it happening a single time. Deny this and you will be completely close-minded and/or deluded.
Can you trust your senses? Sure, most of the times. But sometimes they fail. Take the case of the train you wrote about. Do you know why many people aret hit by trains? Because their senses fooled them. We were not shaped to be used to large fast-moving objects. We evolved in environments where large = slow. Thus, many people just can't figure out how fast the train actually is and the results can be fatal. Want an example? Go to an airport. Check how fast the take-off or landing speeds of an executive jet seems to be when compared with a large jet liner. However, the speeds are not that different. Your brain will, however, give you the impression that the liner is slower than the executive jet.
Are you fully aware of all craft and phenomena on the sky? Are you trained to the point of never being wrong or mistaken? Can anyone honestly claim to be so skilled? I say no.
Two cases to ponder:
Do you think its possible that trained millitary observers, in a crucial combat reccon mission, would confuse a tanker or cargo ship with an aircraft carrier? Note that besides the training, these guys also probably had recognition guides and binoculars.
What would you think of someone remembering seeing in Europe, back in the mid-50´s, a craft looking like a F-16 with canards?
Now, an (anecdotal) example. I am very used to flying. For a number of years, I've been flying the same route twice a week. Most of the times seated by the windows, because I like the view (and its easier to take a nap). Day and night, I'm used to it. I also happen to be very used with it on the ground, since I also made the trip countless times by car or bus. I also made lots of field works at sites along this route. Heck, I am even used to satelliteand geophysical imagery of it. Its safe to say its an axis around which my life revolves since the 80's. I am also a bit of an aviantion buff. I like planes, I like to be informed about them, I like to watch them. And I love the night sky. Whenever I have a chance to look at it, I take it, especially far from city lights.
Does it means I have never been mistaken? No. I've seen lights I have no idea what they were. Heck, sometimes I could not even tell they were on the sky or on the ground! A "sighting" some months ago was very instructive. I still have no idea of what it was. The interesting thing is that I used it to make an experiment. I made a sketch of "the object" as soon as I arrived home and stored it. Every month or so I make an excercise- I remember it the best I can an make a sketch. Then I compare with the first drawing. The differences are startling.
Here's another lesson for you- our memory also can play tricks on us. Your recollections of the experience may no longer be exact.
At last but not least, I must say that fireflys can indeed cause mistakes when flying directly above your head, especially if they are say, 10 or 20 meters away and there are no visual refferences clues. No, I am not saying you saw fireflys. I have no idea of what you actually saw. I just think that jumping to "aliens" is a hell of a jump.